Just imagine krak grenades unerringly hitting their target

Yes. Divine shot applies to your next BS test. Tossing a grenade is a BS test.

Some may argue "its not a shot" but I don't see any problem at all with Divine Shot applying to a thrown weapon.

ItsUncertainWho said:

The only text for divine shot that limits the applicable weapons is: single firearm or other missile weapon

I'd count grenades under "other missile weapon". You would still be limited by the maximum range (4 time base range, meaning 12 times your SB), but if they are within it and not wearing a helmet then you should be able to get your grenade stuck in their eye socket.

TS Luikart, the author of the section of psychic powers, suggested allowing the power only to be used with personal weapons the psyker has had some time to bond with - meaning most heavy weapons and grenades are out.

That is all fine and dandy, but I feel a respectable replacement for an hour's personalization with the obviously single-use grenade would be a speech rattling on about the history, power, and use of the holy hand grenade he is about to lob, which the Emperor itself will guide to its target.

Because impersonating the faithful while using hell-magic is totally not heresy. Honest.